Table 1.
Crossing neutralizing test among QX-like IBV and other serotypes.
| Virus | Serum |
Antigen relatedness value (R) to SZ strain (%)b | |||||
|---|---|---|---|---|---|---|---|
| 4/91 | M41 | SZ | YN | GD | SD | ||
| SZ(QX-like) | 47.8a | 12.3 | 407.4 | 6.17 | 15.8 | 144.5 | 100 |
| SD(QX-like) | – | – | 331.1 | – | – | 141.3 | 91.1 |
| M41(M41-like) | – | 63.1 | 13.8 | – | – | – | 8.1 |
| 4/91(4/91-like) | 61.7 | – | 11.2 | – | – | – | 14.6 |
| YN(YN-like) | – | – | 70.8 | 223.9 | – | – | 6.9 |
| GD(TW-like) | – | – | 11.2 | – | 15.5 | – | 16.7 |
a
Titers were obtained in reciprocal β virus neutralization tests (diluted serum, constant virus).
b
The R values were calculated using the method described by Gravendyck et al. (1996). Criteria for classifying the antigenic relatedness: >0.70, antigenic identity; 0.33–0.70, minor subtype difference; 0.11–0.32, major subtype difference; <0.11, no relatedness (serotype difference).